1. Field of the Invention
This invention relates to a plastic article having a sharp point, and more particularly relates to a medical article for tissue penetration and a method for its preparation.
2. Background
Many articles require a sharp point for penetration of a substrate or a material. Such articles may, for example, be in the form of a solid needle used in sewing or, in the surgical arena, for suturing. In the medical arts, articles having a sharp point, known as lancets, are used to finger prick a patient's skin to draw a small blood sample.
Lancets have been employed for many years to make a quick puncture or penetration of a patient's skin in order to provide a small outflow of blood. Various tests may be employed with only a small amount of blood so that the blood flowing from a finger prick is normally sufficient to carry out a substantial number of tests. However, due to the sensitive nerve endings in the fingertip area, this procedure sometimes induces a significant amount of pain in the patient, even though the skin puncture produces minimal cutting. Moreover, as will be understood, many people are frightened by the appearance of a blade or skin puncturing apparatus of any kind wherein the cutting portion is visible to them prior to the puncture. In order to minimize potential pain, as well as to reduce apprehension in a patient, it is desirable to make the thrust of the lancet through the patient's skin as accurately and rapidly and withdrawal from the skin as quickly and quietly as possible. As a result, a variety of designs for lancets which have structure for automatic thrust and withdrawal have been disclosed, as exemplified by Burns in U.S. Pat. No. 4,677,979.
Hitherto, needles and lancets have primarily been made of metal, most often stainless steel, to impart the desired stiffness and strength. Metal needles, however, are manufactured by a multi-step process which includes drawing a metal rod to the proper size, cutting, sharpening, etching, cleaning, assembling, and connecting to a plastic holder portion. In construction of articles of the type utilized by the medical profession, it is often necessary to connect dissimilar materials. This creates problems in those instances where the dissimilar materials are not readily receptive for interconnection. For example, some plastics such as polytetrafluoroethylene do not bond well to metal components because of the resistance of polytetrafluoroethylene to most epoxies.
It is evident that medical grade articles intended for tissue penetration will of necessity be expensive. For example, a lancet consisting of a stainless steel blade attached to a plastic holder costs about five cents, a prohibitive cost for a single-use, throwaway item used in quantity as is favored in today's medical practice.
Because of the above drawbacks of metal needles and lancets, much effort has been expended in attempts to fabricate these items by single step injection molding of low cost plastics. Applicants are aware of a plastic lancet of injection molded polyacetal. This material, however, is soft and compliant and undesirable for plastic puncture tips because its flexibility requires a substantially perpendicular angle between the point and the finger to prevent bending and unsuccessful puncture. Accordingly, the aforementioned polyacetal lancet is molded in the shape of a tetrahedron to overcome the flexibility. This, however, causes cutting by four edges rather than the two cutting edges of conventional beveled points and leads to increased pain for the patient.
Accordingly, there is a very real need in the medical profession for a lancet capable of penetrating a patient's skin with minimum discomfort yet which is sufficiently inexpensive for economical single use. The present invention is directed to fulfillment of this need.